<!DOCTYPE html>
<!-- 改变第一个 div 元素的背景色为 # bbffaa -->
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
<script type="text/javascript" src="jquery.min.js"></script>
<script type="text/javascript">
	$(function() {
		$("div:first").css("background-color", "blue");
	})
</script>
</head>
<body id="lei">

	<div>1</div>
	<div>2</div>
	<div>3</div>
	<div>4</div>


</body>
</html>